I. Field of the Invention
This invention relates to catalysts and additives therefore generally classified in U.S. Patent Office, Class 55, subclass 3; Class 208, subclasses 52CT, 113, 119, 120, 121, 124, 137, 139, 140, 152, 251R, and 253; Class 209, subclasses 8, 38, 39, and 40; and Class 502, subclasses 5, 20, 21, 38, 515, 516, and 518.
II. Description of the Prior Art
U.S. Pat. No. 4,406,773 (1983) to W. P. Hettinger, et al. discloses magnetic separation of old catalyst from new by a high magnetic field gradient separator (HGMS) which produces a high magnetic field gradient to achieve selective separation.
Subsequent work has uncovered a preferred method of separation involving the use of a magnetic rare earth roller device (RERMS).
U.S. Pat. No. 5,147,527 to Hettinger covers the concept of using a magnetic rare earth roller device (RERMS) for magnetic separation.
U.S. Pat. No. 5,106,486 to Hettinger and Bensley discloses the presence of paramagnetic iron to enhance separation.
U.S. Pat. No. 5,230,869 to Hettinger covers the discovery of a highly superparamagnetic specie, which when present in aged equilibrium catalyst, further improves separation due to its very high magnetic susceptibility compared to normal paramagnetic iron.
U.S. Pat. No. 5,198,098 to Hettinger covers the use of manganese as a "magnetic hook" additive that not only facilitates selective removal of old catalyst, but also serves to reduce activity decline, and improves catalyst performance by reducing coke and hydrogen make and increasing gasoline yield selectivity.
U.S. Pat. No. 5,171,424 to Hettinger teaches the use of highly paramagnetic heavy rare earths as "magnetic hook" additives, and also serves to reduce activity decline and increase catalyst performance.